European Patent Application Publication Number 0 475 213 A1 published 18 Mar. 1992 Bulletin 92/12 (hereinafter "EP Application") based on U.S. patent applications Ser. Nos. 578,697 filed Sep. 4, 1990; 578,696 filed Sep. 4, 1990, and 686,956 filed Apr. 18, 1991, discloses a thermal insulating glazing unit having an edge assembly having low thermal conductivity and a method of making same. In general, The EP Application teaches a thermal insulating glazing unit having a pair of glass sheets about and sealed to an edge assembly to provide a sealed compartment between the sheets. The edge assembly includes a U-shaped spacer frame made of a material that is moisture and/or gas impervious, the spacer frame having a sealant on each of the outer surfaces of the upright legs of the spacer frame and an adhesive bead having desiccant therein adhered to inner surface of the spacer frame. The materials of the edge assembly are selected and sized to provide the edge assembly with a predetermined RES-value as defined and determined in accordance to the EP Application. The EP Application further discloses a thermal insulating glazing unit having three or more sheets with an edge assembly between each of the sheets.
U.S. patent application Ser. No. 08/102,596 filed Aug. 5, 1993, (hereinafter "U.S. Ser. No. 08/102,596") teaches a glazing unit or thermal insulating unit having one or more sheets spaced from and between a pair of outer sheets. In general, the unit includes the pair of outer glass sheets secured to outer legs of a spacer frame having a U-shaped cross section, e.g. of the type taught in the EP Application. On the base of the U-shaped spacer frame between the upright legs is a layer of a pliable material having a groove(s) for receiving edge portions of a sheet(s).
Although the glazing units disclosed in the EP Application and U.S. Ser. No. 08/102,596 are acceptable, it would be beneficial to have a method of manufacturing a glazing unit having three or more sheets that doesn't require providing an edge assembly between sheets as disclosed in the EP application or a groove(s) in a layer of pliable material to receive the edge of the intermediate sheet(s) as disclosed in U.S. Ser. No. 08/102,596.
U.S. Pat. No. 4,149,348 teaches a thermal insulating glazing unit having three or more sheets. In general, the unit includes a pair of outer glass sheets separated by a spacer-dehydrator element, or metal spacer having a generally rectangular cross sectional configuration and having a groove to maintain the intermediate sheet(s) between the pair of outer glass sheets.
Although the glazing unit taught in U.S. Pat. No. 4,149,348 is acceptable, there are limitations. More particularly, the spacer-dehydrator element containing desiccant is formed with a groove, and thereafter the spacer-dehydrator element has to be stored in a dry environment to prevent adsorption of moisture by the desiccant prior to its use. The use of the grooved metal spacer requires additional steps to form the spacer thereby increasing the fabrication cost of the glazing unit.
As can be appreciated, it would be advantageous to provide a glazing unit having three or more sheets and method of making same that supplements, and/or minimizes or eliminates the limitations and/or drawbacks, of presently known glazing units and methods of making them.